US3505020A - Method and composition for detecting free water - Google Patents

Description

United States Patent O 3,505,020 METHOD AND COMPOSITION FOR DETECTING FREE WATER Donald A. Caldwell, Mountainside, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 641,167, May 25, 1967. This application Mar. 5, 1968, Ser. No. 710,642

Int. Cl. C09k 3/00; G01n 31/22, 33/18 US. Cl. 23-230 10 Claims ABSTRACT OF THE DISCLOSURE The presence and extent of dispersed water in aviation turbo-jet fuels and other hydrocarbons is quickly and easily determined by contacting a sample of the hydrocarbon with a small amount of a mixture containing a minor porportion of methylene violet (Color Index 50205) and a major proportion of a finely-divided solid selected from the group consisting of calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate and combinations thereof. The presence of dispersed or free water in the hydrocarbon sample treated in this manner causes the mixed solids in the sample to undergo a change in color according to the amount of free water present.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of my copending application, Ser. No. 641,167, filed May 25, 1967 and now abandoned.

BACKGROUND on THE INVENTION Field of the invention The present invention relates to a novel composition and to the utilization of same to detect the presence and extent of dispersed water in hydrocarbons. More particularly, the present invention is concerned with a mixture of finely-divided solids which when contacted with a hydrocarbon containing dispersed or free water undergoes a change in color according to the amount of free water dispersed in the hydrocarbon.

DESCRIPTION OF THE PRIOR ART Aircraft powered by turbo-jet engines must operate at extreme altitudes during sustained flight in order to obtain maximum fuel utilization. At the temperatures prevailing at such altitudes, any water dispersed in turbo-jet fuel quickly freezes to form ice crystals which may block lines, screens and orifices in the fuel system. Losses in engine power and, in some cases, flame-outs may result. Such difliculties do not arise from water which remains dissolved in turbo-jet fuels. In order to minimize the hazards engendered by dispersed water, the airlines and military services require that aviation turbo-jet fuel be inspected for the presence of dispersed water before it is transferred into the fuel tanks of an aircraft. The inspection procedure generally employed involves the collection of fuel samples from the refueling tank trucks on the flight line and the visual examination of those samples for haze. The presence of haze in such samples is generally indicative of dispersed water but the absence of haze does not necessarily mean that no free water is present. Experience has shown that such fuels may contain considerable quantities of dispersed water even though no haze is discernible and that the conventional inspection procedure is therefore not reliable.

Efforts have been made in the past to develop a simple and yet reliable test which can be used to determine the presence and amount of dispersed water in turbo-jet fuels. By way of illustration of prior art practices, US. 2,968,- 940 describes a method for detecting the presence of dispersed water in hydrocarbons by contacting the hydrocarbon with a solid mixture of barium carbonate and the sodium salt of o-cresolsulfonphthalein. The amount of free water present in the hydrocarbon is disclosed as being proportional to the change in the color intensity of the solids contacted with hydrocarbon.

SUMMARY OF THE INVENTION and a major proportion of a finely-divided substantially anhydrous solid selected from the group consisting of calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate and combinations thereof.

The presence and extent of dispersed water in aviation turbo-jet fuels and other hydrocarbons can be quickly and easily determined by contacting a sample of the hydrocarbon with a small amount of the composition of this invention. The contacting step is preferably carried out by agitating a hydrocarbon sample containing the solid composition and then permitting the solids to settle. The intensity of the color of the solids after settling increases according to the amount of free water dispersed in the sample.

As will be shown hereinlater, the present invention provides a new and improved composition and method for detecting the present and extent of dispersed water in aviation turbo-jet fuels and other hydrocarbons which is considerably more sensitive and reliable than methods employed for this purpose in the past. The method of this invention is accurate to within about 5 parts per million of dispersed water and its accuracy is not adversely affected by the presence of dissolved water or additives commonly employed in turbo-jet fuels and similar materials. Moreover, the color change exhibited by the composition of this invention is not affected by pH within the range of 2-12, by water containing up to 10 wt. percent salt, or by the presence of other alkaline earth substances. Further, the composition of this invention is nontoxic and exhibits a strong visual color in daylight and under incandescent and fluorescent lighting. The composition of this invention may be employed without extensive laboratory equipment, gives results which are readily susceptible of interpretation, and is inexpensive to use.

The mechanisms involved in the method of the invention are not fully understood. It is thought, however, that the color change produced is not due to chemical reactions involving the dye and instead is a physical phenomenon. Apparently a portion of the water-soluble, oilinsoluble dye dissolves if dispersed water is present in the oil and the resulting dye solution spreads in a thin film over the finely-divided solid to thereby produce a color change from white or grayish white to a shade of reddish violet within about 3 minutes or less. If no dispersed water is present, no dye is dissolved and hence the pristine color of the mixed solids remains. Since the amount of dye dissolved increases according to the amount of water dispersed in the sample, the relative intensity of the bright reddish violet produced accurately reflects the water content. It has been observed, however, that both the dye and finely-divided solid of this invention are critical and hence other mechanisms may also be involved.

As pointed out above, the use of the fuchsia dye is critical in the present invention. It has been found that other dyes, including those used as acid-base indicators, are not satisfactory for purposes of the invention for several reasons. In general, water-soluble organic dyes readily react with natural constituents of or additives employed in turbo-jet fuels and other hydrocarbons, thus consuming the dye so that no color change occurs or producing a colored reaction product which masks the true color of the solids used therein. Many such dyes have an additional disadvantage in that they rapidly change color when stored with the finely-divided solid employed as the second constituent of this invention. Such premature color change makes the mixture useless for test purposes. Moreover, many heretofore used dyes when used with the finely-divided solid in the method of this invention 1 do not exhibit a sufficiently wide color difference or sensitivity in the presence of varying amounts of dispersed water and/or do not show strong visual color under natural daylight or incandescent and fluorescent lighting.

The dye of this invention is a water-soluble, oil-insoluble dye which is readily available from commercial sources as a fine anhydrous crystalline powder. It is in this form that the dye is used. In general, however, the dye particles having a diameter in excess of 200 microns ([1,) are not very effective. Accordingly, the major proportion of the dye should have a particle size (diameter) ranging from 1a, or less, up to about 200;/., e.g., a weight average particle size of 44 It is especially preferred that the dye particle size be less than about 74a with about 40-60 wt. percent of the particles having a diameter of less than about 44 The dye is conventionally used in the textile industry for dyeing cotton and silk and is commonly referred to as Methylene Violet, Basic Violet Five, Color Index 50205, fuchsia, etc. A further description of the dye may be found in Color Index, The American Association of Textile Chemists and Colorists, sec. ed. (1956) at 1635 and 3414, which reference is incorporated herein in its entirety by express reference thereto.

The solid material which is intimately mixed with the aforedescribed dye to form the solid composition of this invention is, as indicated above, a finely-divided anhydrous solid selected from the group consisting of calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate, and mixtures thereof. It is preferred, however, to use barium carbonate or calcium carbonate, more preferably the latter. These materials may be in the form of a finely-divided technical grade crystalline powder (e.g., particles smaller than 10,0.) readily available from commercial sources.

In general, the composition of this invention may comprise from about to about 10,000, preferably about 50 to about 2,000, parts by weight of the aforedescribed finely-divided solid for each part by Weight of the dye. The use of about 1 part by weight of the dye and about 400 to 1000 parts by weight of the finely-divided solid has been found to be particularly effective. The amount of the dye-solid mixture added to the sample to be tested may be varied widely, for example, from about 0.05 to about 2.0 grams of mixture per 100 milliliters of hydrocarbon. It is preferred, however, to add from about 0.1

to about 0.5 gram of the mixture to each milliliters of the hydrocarbon to be tested.

In employing the composition of this invention for determining the dispersed or free water content of a hydrocarbon, the color change exhibited by the solids after contact with the hydrocarbon sample may be compared to a color standard. For example, a sample of the hydrocarbon to be tested and a similar or the same hydrocarbon saturated with water but containing no dispersed water are prepared. Predetermined amounts of water are then added to the samples of saturated hydrocarbon containing no dispersed water to serve as standards. Uniform amounts of the dye-solid mixture are then added to the hydrocarbon sample of unknown water content and to each of the standard samples. All of the samples are shaken vigorously for about 10 to 45 seconds and the solids in the sample bottles are then allowed to settle. The color of the solids in the sample of unknown water content is then compared with the colors of the standard samples. The comparison may be conveniently done by visual examination. The dispersed water content of the unknown sample is indicated by the water content of the standard which most nearly matches the unknown sample in color intensity. If desired, accurate determinations can be made, for example, by employing a colorimeter for collating the color of the solids in the sample with predetermined standards.

The test method of the invention may also be employed for determining in the field whether aviation turbo-jet fuels and similar hydrocarbon oils have dispersed water contents which meet predetermined specifications. In order to do this, a particular composition of this invention, an oil sample containing slightly more dispersed water than permitted by the applicable specification, and an oil sample containing slightly less water than the specification permits are prepared. Equal amounts of a particular composition of this invention are added to a sample of the oil to be tested and to each of the samples containing known amounts of dispersed water. Each sample is then agitated and the solids therein are permitted to settle. The intensity of the color of the solids in the test sample is compared with that of the solids in the two prepared samples and from this comparison it is determined whether the fuel contains more or less than the allowable quantity of water. Again the color intensity comparison may be carried out by visual examination but more accurate results can be obtained by means of a colorimeter or a similar device.

In lieu of preparing standard samples each time an unknown is tested in the manner described above, in many cases it may be preferable to photograph standard samples and employ the pictures or swatches of corresponding color as a basis for comparison in future tests. This procedure somewhat simplifies carrying out the test under field conditions.

For ease of handling and in order to facilitate the carrying out of the method of the invention, it will generally be found convenient to blend the dye-solid mixture for a time sufficient to obtain homogenity (e.g., 2-5 minutes) and to thereafter package the mixed dye and solid in capsules or ampules. Each capsule or ampule may contain sufficient material for one test. For relatively short periods of time it is sufficient to store the capsules in a tightly closed glass jar. Where the capsules are to be stored for extended periods of time or under severe weather conditions, it may be preferred to maintain them in a sealed vessel in the presence of a desiccant. Indefinite storage is possible by using sealed glass ampules.

The invention can be more fully understood by reference to the following examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 As indicated previously, the composition of this invention was discovered after evaluating and testing a large of about 10 seconds. After standing for 1 or 2 minutes, the intensity of the color of the solids was noted. The comparative results are given below in Table II.

TABLE IL-FREE WATER DETECTION TEST Grams of Composition of indicator mixture indicator 1 mixture 1 minute reading 2 minute reading Finely-divided solid Dye per 100 cc. of free water free water hydrocarbon Compound 3 Amt, mg. Compound 4 Amt., mg. sample 2 15 p.p.m. 45 p.p.m. 15 p.p.m. 45 p.p.m.

100 Cresol Red 500 0. 5 0 1 2 100 Fuchsia 500 O. 1 3 2 4 100 Cresol Red 2, 000 0. 125 1 1 l l 100 Fuchsia 2, 000 0. 125 1 2 1 3 100 0. 5 0 1 1 2 50 0. 5 0 l 0 1+ 250 0.5 0 2+ 1 2+ 500 0. 5 0 3 1+ 4 1 Rating scale range=05; wherein 0 indicates no visible color change; 1 indicates a barely perceptible color change; 2 indicates a definite color change; and 3, 4 and 5 indicate an increasingly stronger color change.

2 A commercial kerosene-type aviation fuel as described in ASTM D-1665.

3 Average particle size (diameter) of 2-3 4 Average particle size of cresol red is less than 150p;

ticles have a diameter greater than 74g, percent have a diameter less than 44p.

TIONS FOR USE IN DETECTING THE PRESENCE OF DISPERSED WATER IN HYDROCARBONS Indicator composition Finely-divided Deficiency of dye or indicator Dye solid adsorbent composition Cresol Red BaCOa, BaSOa, Does not give true red color CaC 03.

when pH of Water is below 8 Poor color difierence vs. free water content.

Amaranth BaC O MgC Os, Mixture red before use; poor Mg(OH2), MgO. color difference in test. Anthraquinone Poor solubility in H O; color Violet R. too blue.

Azofuchsia 6B Color aflected by PIT of water.

Azorubin Various. Discolors powder mixture.

Bordeaux Red BaCOs Poor color difference; color changed by 10% salt in water.

Chromotrope 6B Color affected by pH; color intensity not strong.

Fast Red S Various Reacts with alkaline earths;

color fades.

Ponceau S Aflefited by pH; reacts with Safranin O Various Reacts with salt; discolors solid mixture.

Acid Fuchsia do Color fades rapidly with alkaline earth. I

Basic Fuchsia do Becomes insoluble in water in presence of alkahne Cr stal Violet 0 or a co e y p Pollceau 2R Inhibits settling of solid.

Congo Red. Changes color with pH.

Phenosafranin Color too orange; fades,

aifected by pH. Neutral Red Changes color with pH.

Example 2 To show the advantage of the composition and method of this invention over a widely accepted commercial method (i.e., US. 2,968,940), sensitivity comparisons were made on various samples which included the composition of this invention and the prior art composition used for the detection of free water in hydrocarbon fuels.

In the test conducted, a commercial kerosene-type aviation fuel meeting the requirements of ASTM Specification D-l655 was saturated with water by storage in a container with an excess of free water adsorbed on filter paper for 48 hours. A number of samples were then prepared by adding p.p.m. or 45 p.p.m. of water to the saturated hydrocarbon. Various amounts of anhydrous sodium salt of o-cresolsulfonphthalein (i.e., cresol red) anhydrous barium carbonate mixtures, fuchsia/ anhydrous barium carbonate mixtures or fuchsia/ anhydrous calcium carbonate mixtures were added to 100 cc. portions of the test fuel. Each of the samples was then shaken for a period fuchsia has a particle size distribution wherein 21 wt. percent of the par- 23 wt. percent have a diameter within the range between about 44;. and 74p; and 56 wt.

From Table II it can be seen that the color difference afforded by the compositions of this invention is substantially greater than that obtained by the use of the prior art mixture. In other words, a much greater color difference was observed for the fuchsia-calcium carbonate mixtures and fuchsia-barium carbonate mixtures which were contacted with the fuels containing 15 p.p.m. and 45 p.p.m. of water. Such greater color difference results in a greater sensitivity which makes possible the more accurate determination of the water content as compared to the utilization of the prior art mixture.

Further, it is readily apparent that the improved sensitivity exhibited by the compounds of this invention 'makes these compounds especially useful in an on site inspection test for the presence of dispersed water in a turbo-jet fuel before the fuel is transferred into the fuel tank of an airplane. For example, a go-no-go test to determine whether a sample of an aviation turbo-jet fuel contains more or less than 30 parts per million of dispersed Water is carried out by adding a composition of this invention, e.g., fuchsia-calcium carbonate, to the sample to be tested in accordance with the method outlined in the previous example. The color of the fuchsiacalcium carbonate mixed solids in the test sample is then compared with the color exhibited by the mixed solids in standard samples containing 15, 30 and 45 p.p.m. of free water or with color swatches representing standard samples. A simple visual comparison may then be made to determine whether the fuel contains more or less than 30 parts per million of free water.

What is claimed is:

1. A composition useful for detecting the presence of free water in hydrocarbons, which comprises methylene violet and a finely-divided anhydrous solid selected from the group consisting of calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate and combinations thereof; the weight ratio of said solid to methylene violet being within the range between about 20:1 and 10.00021.

2. A method for detecting the presence of dispersed water in hydrocarbons which comprises contacting said hydrocarbons with a minor proportion of the composition of claim 1 whereby said composition undergoes a change in color in the presence of free water.

3. The composition of claim 1 wherein the major proportions of the methylene violet has an average particle size less than about 200 microns.

4. The composition of claim 3 wherein the finelydivided solid is selected from the group consisting of calcium carbonate and barium carbonate.

5. The composition of claim 4 wherein the weight ratio of said finely-divided solid to methylene violet is within the range between about :1 and 2,000: l.

6. A method for detecting the presence of dispersed water in hydrocarbons, which comprises contacting said hydrocarbons with a minor proportion of the composition of claim 5.

7. The composition of claim 5 wherein the finelydivided solid is calcium carbonate.

8. The composition of claim 7 wherein the methylene violet has an average particle size less than about 74 microns with about 40%60% by weight of the particles having a diameter of less than about 44 microns.

9. The composition of claim 8 wherein the weight ratio of said finely-divided solid to methylene violet is Within the range between about 400:1 and 1,000: 1.

10. A method for determining the presence and extent of dispersed water in a hydrocarbon, which comprises adding from about 0.1 to about 0.5 grams of the composition of claim 8 to about 100 milliliters of a hydrocarbon sample; then agitating said sample; thereafter permitting solids to settle in said sample; and comparing the color of the settled solids with a predetermined standard.

References Cited UNITED STATES PATENTS 1/1961 Feldman et al.

OTHER REFERENCES Color Index, The American Association of Textile Chemists and Colorists, sec. ed (1956) pp. 3414, 1635.

MORRIS O. WOLK, Primary Examiner R. M. REESE, Assistant Examiner US. Cl. X.R.